External beam radiation therapy (also called radiotherapy) involves a series of daily treatments
to accurately deliver radiation to the prostate. Research has shown that higher doses of radiation can improve cure rates. Modern radiation
therapy is as effective as surgery to cure prostate cancer.
Before treatment begins your radiation oncologist will develop a treatment plan using information from your biopsy, imaging and physical exam.
A CT scan is done in the position you will be treated, often with a supportive device to keep you comfortably in the same position for treatment.
This is often called simulation. Sometimes your treatment plan will include not only the prostate, but the seminal vesicles (glands on the
back of the prostate) and lymph nodes. Ask your doctor to explain what treatment area is appropriate for you.
With CT scans, 3-D targets of the prostate and normal tissues are created. These treatment plans focus radiation beams on the prostate while limiting
radiation to healthy tissues around it such as the bladder and rectum. Intensity modulated radiation therapy (IMRT) and
image guided radiation therapy (IGRT) are treatment approaches that allow the radiation
beams to treat the cancer and lessen the risks of side effects.
External beam radiation therapy can be delivered using a variety of techniques. In most cases, external radiation is in the form of high-energy
photons, or X-rays. In a few clinics in the country, proton beam therapy is used to treat prostate cancer. Proton therapy is a form of external
beam radiation therapy that uses protons rather than photons to treat cancer cells.
With all external beam therapy, treatment is delivered in a series of daily sessions, Monday through Friday, for several weeks. Each treatment
is painless and similar to a long X-ray: you hear noise but will feel nothing.
The length of your treatment will depend on your health and the type of radiation used. The use of even shorter schedules of external beam radiation
therapy is being studied for patients with early-stage prostate cancer.
Hypofractionated radiation is a form of daily treatment giving higher doses over four to six weeks compared to a more standard
treatment time of seven to nine weeks. Stereotactic body radiation therapy (SBRT) is a technique
for treating cancers in five or fewer treatments at substantially higher doses. Hypofractionated and stereotactic radiation are currently being
evaluated for long-term data and may be considered for certain patients.